Exhume

Two mana to put a creature from the graveyard onto the battlefield, no targeting clause, no upkeep cost, no life payment: the rate is absurd, and the "each player" wording is the only thing standing between it and a strictly broken spell. Reanimator decks paid that tax by making it cost nothing. The whole gambit is arranging the disparity before the spell ever resolves: discard a fatty with a loot effect, fill your own yard with self-mill or dredge, and cast this while the opponent's graveyard is empty or holding a 2/2 worth less than nothing to reanimate. The symmetric clause becomes a rounding error you control. Animate Dead and Reanimate each target one creature and accept a real cost (a debuff aura, a chunk of life) for the privilege; this one's downside is purely contingent, contingent on facing a mirror of your own plan. The arithmetic is what makes the deck exist: it converts a discarded threat into a battlefield presence for two mana, a fraction of casting that threat honestly, and the gap between those two numbers is the entire engine. The cost discipline lives in the setup rather than the card. You owe nothing to the symmetry as long as you are the only player at the table who did the work of being ready to break it.